30 



MAZATLAN BIVALVES 



Smallest specimen measures long. '04, lat. '06, alt. '02. 



Largest 49, '72, '24. 



Tablet 101 contains 3 young valves. 102, the largest (imper- 

 fect) specimen. 103, a C. lameJosa, which had established 

 itself within the empty remains of a Petr. robusta, which had 

 itself gone to dwell inside the skeleton of a deceased relative 

 which had originally constructed the burrow.* 



The form coarctata was found by Mr. Hanley in Spondylus 

 Lamarckii ; Havre Col. 



43. ClTMINGIA TKIGONULABIS, Sow. 



Proc. Zool Soc. 1833, p. 35. Eve. Conch. Syst. pi. 49, f. 2. 



C. B. Ad. Pan. Shells, p. 288, no. 480. 

 Lavignon trigonularis, Gray. B. M. Cat. I? Orb. Moll. p. 59, 



no. 519. 



Tolerably well distinguished by the great projection of the 

 ligamental spoon and hinge teeth. The laterals are very short, 

 truncated, and of nearly equal length. Pallial sinus very large. 

 Decussating striae well developed. JST. B. The muscular scars 

 often vary in shape with the distortions of the shell. The 

 largest specimen found measures long. '5, lat. '62, all. "32. 

 Hob. St. Elena : among stones in deep water, Cuming. 

 Ecuador ; St. Elena, D" OMgny. Panama, very rare, C. B. 

 Adams. Mazatlan : nestling in burrows in Spondylus Lam- 

 arckii ; very rare ; L'pool fy Havre Coll. 

 Tablet 104 contains 1 perfect and 3 broken specimens, of 

 various ages. 



44. CUMINGIA CALIFOENICA, Conr. 



Journ. Ac. Nat. Sc. Phil. 18 , p. 

 Teeth andpallial sinus intermediate between C- lamellosa and 



C. trigonularis. Anterior side generally swollen. The largest 



specimen found measures long. '33, lat. '52, alt. '22. 



Hob. Upper California, Nuttall. Mazatlan ; nestling in bur- 

 rows in Spondylus Lamarckii, very rare ; L'pool Col. 

 Tablet 105 contains 1 young, and 2 adult specimens. 



* So I ha\e, in limestone from Weymouth Bay, Sphsenia Binghami nestling in 

 the tube of a Gastrocheena modiolma which had been formed by soldering 

 together portions of a Thracia distorta through which it had burrowed. 



